Mitosis and Meiosis

Question 1

Mitosis is

Answer 1

nuclear division without genetic change. it has 4 stages:
prophase, metaphase, Anaphase and Telophase.
PMAT.
mitosis varies among eukaryotes ! here are the stages in the animal cell

Question 2

What is prophase?

Answer 2

condensation of chromatin into chromosomes. centrioles located in the centrosome move to the opposite ends of the cells. first the nucleolus and then the nucleus disappear. the spindle apparatus begins to form consisting of aster (microtubules radiating from the aster)., kinetochore microtubules growing from the centromeres (a group of proteins located toward the centre of chromosome and spindle microtubules connecting the two centrioles.

Question 3

what happens in metaphase?

Answer 3

chromosomes align along the equator of the cell

Question 4

what happens in anaphase?

Answer 4

begins when sister chromatids split at their attaching centromeres and move toward opp ends of the cell.
cytokinesis : the actual separation of the cellular cytoplasm due to constriction of microfilaments about the centre of the cell , may commence toward the end of this phase.

Question 5

what happens in telophase?

Answer 5

the nuclear membrane reforms followed by the reformation of the nucleolus. chromosomes decodes and become difficult to see under the microscope. cytokinesis occur.

Question 6

what does mitosis result in?

Answer 6

genetically identical daughter cells

Question 7

What is meiosis?

Answer 7

a double nucleur division which produces four haploid gametes (also called germ cells).

Question 8

In humans which cells undergo meiosis?

Answer 8

spermatogonium and oogonium ! rest are somatic cells and they undergo mitosis.

Question 9

Meiosis 1 proceeds similarly to mitosis with differences

Answer 9

Prophase 1 : homologous chromosomes line up along side each other , matching their genes exactly. - crossing over might occur here ( exchange sequences of DNA nucleotides) . homologous chromosomes here have four chromatids and are called tetrads.

Question 10

what happens in metaphase 1?

Answer 10

homologues remain attatched and move to the metaphase plate. rather then single chromosomes aligned along the plate as in mitosis, tetrads align in meiosis.

Question 11

What happens in anaphase 1?

Answer 11

separates the homologues from their partners.

Question 12

what happens in telophase 1?

Answer 12

a nucleur mem may or may not reform and cytokinesis may or may not occur.

Question 13

meiosis 1 is a ___ division

Answer 13

reductive

Question 14

what happens in meiosis 2?

Answer 14

proceeds with prophase 2, metaphase 2, anaphase 2 and telophase 2 appearing under the light microscope much like normal mitosis.

Question 15

what are the final products?

Answer 15

haploid gametes each with 23 chromosomes. in the case of spermatocyte 4 sperm cells are made and in case of oocyte , single ovum is formed. In the female, telophase 2 produces one gamete and a second polar body.

Question 16

non disjunction

Answer 16

if during anaphase 1 or 2, the centromere of any chromosome does not split this is called non disjunction. if that occurs in anaphase 1 , one of the cells will have 2 extra chromatids and the other will be missing a chromosome. (this extra chromosome will line up in metaphase and behave normally in meiosis 2). if this happens in anaphase 2, one cell will have one extra chromatid and one will be missing one.